1. Field of the Invention:
The present invention relates to a control system for positioning a plurality of work pieces in registration with a plurality of corresponding target positions on another work piece within a confined range and, more particularly, to a technique for positioning the respective axes of multi-spindle tools, such as the multi-spindle screw drivers of a screw driving machine, into registration with a plurality of holes in a work piece, such as a flange.
2. Description of the Prior Art:
Because of the difficulties in automating the assembly operation of a production line, the assembly operation has been carried out manually. One of the techniques employed for assembling a plurality of parts together into one united functional component is the screw driving technique, wherein, manually, a screw is inserted into a hole and then the screw is tightened mechanically, through the use of a tool such as a screw driver. While proposals have been made for automating the screw tightening operation by the use of an automatic screw tightening machine in combination with a mechanism for bringing a hole in a work piece into registration with a screw position therefor, difficulties in the practical application of this technique have arisen in that there has not been a saving in man power and strict accuracy in the positioning mechanism is necessary.
In general, in a workpiece, there are the plurality of screw holes which are to come into registration with holes in another work piece such as a flange, for receiving screws and it is common practice to prepare the screw holes with high accuracy in terms of the relative positions. Yet, there remains the problem of positioning a work piece such as a flange in a screw tightening machine, because of the relative positional variation of the flange even if the hole positions for the screws to be inserted therein are provided accurately.
Accordingly, the complete registration of screw positions in a multi-spindle screw tightening machine with the corresponding positions of a plurality of such holes has resulted in a considerable amount of difficulty.